Electrochemical Cells and Thermodynamics
Define the following terms: faraday, salt bridge, anode, cathode, soltaic cell, and electrolytic cell
The Correct Answer and Explanation is :
Definitions:
- Faraday (F):
Faraday is the unit of electric charge that is equivalent to the charge of one mole of electrons. It is approximately 96,485 Coulombs (C). This constant is used in electrochemical calculations to relate the amount of electric charge transferred during a redox reaction to the amount of substance involved. - Salt Bridge:
A salt bridge is a U-shaped tube containing a salt solution (often potassium chloride or potassium nitrate) that connects the two half-cells of an electrochemical cell. It serves to complete the electrical circuit by allowing the flow of ions between the two half-cells, thus maintaining the neutrality of the solutions and preventing the buildup of charge that would otherwise halt the reaction. - Anode:
The anode is the electrode at which oxidation occurs in an electrochemical cell. In a galvanic (voltaic) cell, the anode is the negative terminal, where electrons are released into the external circuit. In an electrolytic cell, the anode is the positive terminal where electrons are drawn away. - Cathode:
The cathode is the electrode where reduction occurs. In a galvanic cell, it is the positive terminal, where electrons from the external circuit are gained. In an electrolytic cell, the cathode is the negative terminal, where reduction takes place. - Galvanic (Voltaic) Cell:
A galvanic or voltaic cell is an electrochemical cell that generates electrical energy from spontaneous redox reactions. It consists of two half-cells connected by a salt bridge or porous partition, with one electrode acting as the anode (oxidation) and the other as the cathode (reduction). An example is the common battery. - Electrolytic Cell:
An electrolytic cell is an electrochemical cell that uses electrical energy to drive a non-spontaneous reaction. This type of cell requires an external power source to induce the chemical changes, such as in electroplating or the electrolysis of water to produce hydrogen and oxygen.
Explanation:
Electrochemical cells, whether galvanic or electrolytic, involve the transfer of electrons between two electrodes where redox reactions occur. In a galvanic cell, such as a battery, the cell spontaneously produces electrical energy from a redox reaction. Oxidation takes place at the anode, where electrons are released, while reduction occurs at the cathode, where electrons are gained. A salt bridge or porous partition is critical to maintaining the cell’s electrical neutrality by allowing the flow of ions between the two half-cells.
In an electrolytic cell, the process is reversed. Here, an external electrical current is applied to drive a non-spontaneous reaction, such as the decomposition of compounds. The anode is connected to the positive terminal of the external power source, and oxidation occurs there, while the cathode, connected to the negative terminal, facilitates reduction.
The Faraday constant relates the quantity of electric charge transferred in a given reaction to the amount of substance involved, helping quantify these processes. Thus, electrochemical cells and thermodynamics are deeply intertwined, with the Faraday constant serving as a key link in calculating the potential and energy changes in these systems.
